This work presents an overview of some recent developments made by the authors in the field of vibrational control of largescale structural systems subject to seismic excitations. The structural systems under consideration are classified in two broad categories: (i) high-rise buildings, and (ii) multi-building systems. When dealing with high-rise buildings, the inclusion principle can be used as a powerful mathematical tool to design semi-decentralized state-feedback and output-feedback controllers. In the case of multi-building systems, a passive-active structural vibration control for adjacent buildings consisting in a combination of passive linking elements with an active decentralized control system is designed. Numerical simulations show that the overall active-passive control system achieves excellent results when the active control system works; in case of full or partial failure of the active control system, a remarkable reduction in the vibrational response is guaranteed by the passive linking elements. Three different building models serve as example to clarify the theoretical results and, at the same time, to show the advantages of the proposed control approaches